JPH1012684A - Method and equipment for inspecting semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inspecting method using a scanning electron microscope and an equipment for it with which an electron beam which is stable extending over a long time is obtained for a sample without being affected by charging-up. SOLUTION: Charging-up is controlled by irradiating the surface of a sample wafer with an electron shower and an ion shower. Charging-up is controlled with a controlling calculator 20 according to an inspection condition and a material quality of the sample, etc. A stable electron beam image wherein a condition of charging-up does not charge is inputted with a secondary electron detector 15, and then compared/inspected at a picture processing part 19, to detect a defect of a semiconductor device. By this, an influence on the electron bean image due to charging-up of the surface of the sample is avoided, and a stable inspection extending over a long time is realized with the electron beam image. Further, by feeding an inspection result back to a semiconductor manufacturing process, a defective coefficient of the semiconductor device is reduced, and reliability is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a technique for inspecting a pattern of a semiconductor device using an electronic scanning microscope.

[0002]

2. Description of the Related Art As shown in FIG. 1, a manufacturing process of a semiconductor device includes a number of pattern forming steps. Each pattern is formed by the steps of film formation, photosensitive resist coating, exposure, development, etching, resist removal, and cleaning. If the manufacturing conditions are not optimized in each of these steps, the circuit pattern of the semiconductor device will not be formed properly, and if the pattern is chipped or deformed, defective products will be generated. These semiconductor devices are electrically inspected after the completion of the wafer processing process, and the cause of the failure is investigated by a method such as fail bit analysis and countermeasures are taken. However, such a method has a disadvantage that even if a defect occurs during the manufacturing process, the defect cannot be detected until the product has completed the wafer processing step. Since it takes time, such a method has a problem that a large number of defective products are manufactured without taking measures against defects.

On the other hand, as shown in FIG. 1, in each step of the manufacturing process, if a product is inspected during the manufacturing process,
Even when a pattern defect occurs due to a device failure or the like, the cause can be investigated and measures can be taken at an early stage. As a result, the ratio of defective products can be reduced and production efficiency can be improved, which can greatly contribute to improving profits.

In the process of manufacturing such a semiconductor device, a defect inspection of a circuit pattern on a wafer is performed by comparing a pattern to be inspected with a non-defective pattern or a similar pattern on a wafer to be inspected, and has a size of 0.5 μm. Many inspection apparatuses using optical microscope images capable of detecting defects of a certain degree have been put to practical use. The circuit pattern structure of semiconductor devices is very fine, and many products with dimensions of 1 μm or less are already manufactured.Therefore, there is a need for inspection technology that can detect foreign substances and defects with dimensions of 0.1 μm or less. Is growing. Compared with conventional optical microscopes, electron microscopes can obtain a higher resolution in principle, and therefore, it is expected that such a semiconductor device is compatible with miniaturization. Further, there is a problem that abnormal oxidation due to poor drying during washing and optically transparent materials such as resist are difficult to observe with a conventional optical microscope. On the other hand, since an electron beam image by an electron microscope generally observes only the surface, a pattern inspection can be performed on a transparent material or a material having a low reflectance. For these reasons, a highly sensitive inspection technique using an electron microscope image has been developed.

An electron microscope can obtain a high-resolution image, but has a problem that the quality of the image is unstablely changed due to a charging phenomenon peculiar to the electron microscope. This is because the sample surface is charged by electron beam irradiation and the secondary electron emission efficiency changes, which changes the quality of the obtained electron beam image. As the sample surface charges progress, the primary beam is deflected to deflect the image. May be distorted. This charging phenomenon occurs when the sample is an insulating material, and generally poses a serious problem in circuit pattern inspection of a semiconductor device in which the insulating material is frequently used.

FIG. 2 shows an example of a change in an electron beam image due to such a charging phenomenon. When the inspected wafers are sequentially inspected in the order indicated by the arrows in FIG. 2, the charged state of the sample surface changes depending on the imaging location and time, so that the obtained electron beam image also changes. In FIG. 2, the brightness and the contrast of the pattern of the electron beam image change in 5 and 6, and the size of the pattern changes in 7 as well. In the case of defect inspection using an electron beam image, as shown in FIG. 2, since the electron beam image fluctuates with time due to charge-up on the sample surface or the like, the image is spatially differentiated once and the effect of brightness drift. It was necessary to perform processing such as reducing the number of images and compare the images.

Further, not only the brightness but also the shape may change with time as shown in 7 in FIG. 2. In such a case, a process corresponding to the change in shape is required.
When there is such a time variation of the electron beam image, the electron beam image obtained during the long-term inspection changes, so that the comparative inspection of the entire wafer is difficult, and the defect distribution in the wafer is obtained. There is a problem that you can not do. The appearance inspection of circuit patterns in the manufacturing process of semiconductor devices detects defects that occur at random, so inspection over the entire wafer is often required, and the distribution of defects in the wafer is very effective in determining the cause of defect occurrence Information. Inspection under stable conditions is always indispensable to monitor the semiconductor device manufacturing process and to find defects in manufacturing conditions such as pattern exposure conditions at an early stage.

Japanese Patent Application Laid-Open No. 63-218803 discloses a means for obtaining an electron beam image while the charge-up of a sample is always the same. This is to always obtain an electron beam image under the same charging condition by always inputting an electron beam image at a fixed time from the start of electron beam irradiation, but this is a sudden electron beam image after electron beam irradiation. It is a means for responding to changes, and cannot respond to a global change in the state of charge that occurs over the entire wafer due to long-term inspection, so that a long-term inspection cannot provide a stable electron beam image. There is a problem.

[0009]

As described above, when the brightness of an electron beam image greatly changes, such as a change or inversion of contrast, inspection cannot be performed by simple contrast comparison, and it is often used in image processing. It is very difficult to set the threshold value even if the electron beam image fluctuates with time even in the threshold processing performed. If only the brightness of the electron beam image changes,
The effect of brightness fluctuation can be reduced by processing such as using a spatial differential image, but since spatial differential processing emphasizes random noise contained in the image, such noise is erroneously recognized as a defect. Would. FIG.
If the pattern shape changes as in 7 above, it is necessary to perform processing to allow the change in shape, but if the allowable width is large, it is difficult to detect defects such as actual pattern thinning Becomes Such defects are often caused by fluctuations in the manufacturing process, and it is necessary to find out and take countermeasures at an early stage, and omission of detection is not allowed.

An object of the present invention is to provide a means for controlling the state of charge-up on a sample, thereby suppressing changes in brightness and shape of an electron beam image and obtaining a stable electron beam image even in a long-term inspection. Accordingly, it is an object of the present invention to realize a highly sensitive and highly reliable inspection apparatus.

[0011]

The above object is achieved by always obtaining an electron beam image under the same conditions by controlling and maintaining a constant charge state at an electron beam irradiation position on a wafer to be inspected. .

FIG. 3 shows how the charged state of the sample is changed by the scanning of the electron beam. a) shows that the pattern is not charged, and b) shows that the state of charge of the pattern is changed by electron beam scanning when electric charge is accumulated on the pattern. In this manner, the charge is accumulated on the sample by the scanning of the electron beam or the accumulated charge is diffused, thereby causing non-uniform charging on the wafer to be inspected, and as shown in FIG. A change such as a brightness shape occurs in the line image. However, when the charge on the sample is in a saturated state as shown in FIG. 3C), even if the electron beam is further scanned on the pattern, the charged state on the sample does not change. Also, by always keeping the potential of the sample constant, it is possible to obtain an image in a state where charging is not always generated.

As described above, the charge state is controlled by intentionally charging the sample in advance, saturating the charge on the sample, or imparting a positive or negative charge to the sample surface so that the charge accumulated on the sample surface is not changed. This is done by summing or by always keeping the sample constant at ground potential by grounding. In addition, by performing these operations at a predetermined timing with respect to image input during the inspection, it is expected that the charge on the sample is always in the same state, and the image input of the sample can be performed with almost the same charge every time. . Further, since the electron beam image changes due to the change in the charged state, the charged state of the sample can be monitored using the electron beam image obtained during the inspection.

At this time, the state of charging on the sample depends on the type of the object to be inspected, such as the material and shape, and inspection conditions such as the acceleration voltage of the electron beam. A means for determining the control method is also required.

In this way, the electron beam image at each inspection position on the wafer can always be input under the same conditions even in the inspection for a long time. Therefore, even in an image taken at a long interval or an image taken between different wafers, an image of the same pattern becomes almost the same except for a defective portion. Therefore, even in an inspection apparatus which compares these and detects a defective portion from the difference, it is possible to easily detect only the defective portion from the difference signal of the image.
As a result, a non-defective part is less likely to be mistaken for a defect, and high detection sensitivity can be realized even in a long-time inspection. In addition, since a stable image can be always obtained, a long-term inspection can be performed, and an inspection of the entire surface of the wafer or an inspection between wafers can be realized. By realizing such an inspection apparatus, it is possible to promptly investigate the cause of the occurrence of a defect and take countermeasures in a semiconductor manufacturing process, and as a result, it is possible to contribute to an improvement in product yield.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. FIG. 4 is a configuration diagram of a semiconductor pattern inspection apparatus according to the present invention. The narrowed electron beam 8 emitted from the electron source 13 is deflected by the deflector 14, and can scan the upper surface of the semiconductor wafer 1 as a sample in an arbitrary order.
A secondary electron signal generated from the inspection target wafer 1 irradiated with the electron beam is detected by a secondary electron detector 15 and is output to an image input unit.
16 is input as an image signal. Inspection wafer is XY
It can be moved by the stage 17, and irradiation of an electron beam and image input synchronized with the movement of the stage are possible.

Based on the image signal and the inspection position information detected by the stage position measuring unit 18, the non-defective pattern stored in advance by the image processing unit 19, a different place on the wafer to be inspected, or a similar pattern on a different wafer is used. The defect is determined by comparison. The operations of the electron optical system and the XY stage are controlled by the control computer 20. Beforehand, the product name and process name of the wafer to be inspected, the accelerating voltage of the electron beam,
Conditions such as a scanning position / speed, a stage moving position / speed, and signal detection timing are input.

Reference numeral 21 denotes an electron shower generator, which can negatively charge the sample surface by irradiating electrons. Reference numeral 22 denotes a mesh electrode, which prevents electrons from the electron shower emitted from the electron shower generator 21 from being detected by the secondary electron detector 15 and enables detection of only secondary electrons.

Reference numeral 23 denotes an ion shower generator, which can positively charge the sample surface by irradiating ions.
The electron shower generator 21 and the ion shower generator 23 can be controlled by the control computer 20, and the amount of irradiation of electrons and ions, the irradiation energy of the electron shower, the voltage of the mesh electrode, and the like are set to appropriate values according to the type of the test sample. Then, the charging state of the sample surface is controlled by appropriately turning on / off the respective functions. The control method of the charged state can be manually set by the control computer, but can be automatically set by the inspection condition input to the control computer in advance.

Further, a needle 25 for grounding is attached to the wafer chuck 24 so as to come into contact with the wafer 1 to be inspected, so that the sample substrate is always kept at the ground potential.

With such an apparatus configuration, the charged state of the sample surface is controlled, and a pattern inspection with an always stable electron beam image with little time fluctuation is realized.

Next, a more detailed embodiment of the method for controlling the charge amount will be described. FIG. 5 shows the dependence of the secondary electron emission capacity and the beam diameter on the primary electron acceleration energy.
The secondary electron emission capacity varies depending on the material of the sample, but it is almost 50
It takes the maximum value between 0 eV and 1000 eV. Under the inspection condition 26 in which the secondary electron emission ability becomes 1 or more, the number of secondary electrons emitted from the sample exceeds the number of incident primary electrons, so that the sample surface is positively charged and the secondary electron emission ability is 1 or less. Under condition 27, the charge is negative.

Therefore, in FIG.
In the region 26 where the secondary electron emission capacity becomes 1 or more, a negative shower electron charge 29 by an electron shower 28 is applied to the sample surface as shown in FIG. In a region 27 where is equal to or less than 1, by applying a positive shower ion charge 29 by an ion shower 30 as shown in FIG. 7, the sample is prevented from being charged, and a stable secondary electron image is obtained.

As shown in FIG. 5, since the beam diameter depends on the primary electron acceleration energy, a desired beam diameter is determined at the time of inspection, and charge control is performed using the secondary electron emission ability of the sample under the conditions. Choose the right way. The secondary electron emission ability is determined based on the material of the sample surface and the like.

FIG. 8 is a detailed embodiment of a method for controlling charging by an electron shower. As mentioned in the previous example,
When the secondary electron emission ability is 1 or more, a negative charge is applied to the sample surface to stably maintain the charged state on the sample surface. At this time, in order to prevent both the electron shower 28 and the secondary electrons 32 irradiated by the electron shower from being detected by the secondary electron detector, the electrons irradiated by the electron shower are blocked by the mesh electrode 22.

FIG. 9 shows the energy distribution of emitted electrons. A secondary electron image can be obtained by detecting electrons having an emission energy of about 10 eV. As a result, a voltage is applied to the mesh electrode so that electrons having an emitted electron energy of several eV or less smaller than the peak of the emitted energy of the secondary electrons are not detected by the secondary electron detector, and the energy filter 33
By irradiating the sample surface with the electron shower generator generating low energy electrons that cannot pass through the mesh electrode and irradiating the sample surface, it is possible to detect only the secondary electrons. it can.

The irradiation amount of the electron shower, the energy, and the voltage applied to the mesh electrode are set to appropriate values by a control computer according to the sample. Similarly, when a backscattered electron image is input, only the backscattered electrons are detected.
The energy of the electron shower and the voltage of the mesh electrode may be set.

FIG. 10 is a detailed embodiment of a method for controlling charging by an ion shower. As described in the previous embodiment, when the secondary electron emission ability is 1 or less, a positive charge is applied to the sample surface to stably maintain the charged state of the sample surface. At this time, the irradiation amount of the ion shower is set to an appropriate value by the control computer according to the sample. By irradiating these electron showers or ion showers at the time of electron beam image input and keeping the sample surface always in the same charged state, electron beam images under the same conditions can be obtained,
A comparative inspection can be performed even in a long-time inspection.

In the case of a sample having a relatively long time from the start of electron beam irradiation to charge-up, the inspection area is sufficiently irradiated with an electron or ion shower before the start of inspection to charge the sample surface. By starting the input of the electron beam image after the state of is saturated, a stable electron beam image can be obtained. At this time, the timing of the irradiation of these ions or electron showers and the input of the electron beam image is determined to an appropriate value using the conductivity of the pattern to be inspected.

A sample having a relatively high conductivity has a high rate of diffusion of the charges incident on the sample, and the accumulation of charges can be prevented by always keeping the potential in the wafer to be inspected at the ground potential by grounding. In addition, a change in an electron beam image due to charging can be prevented.

FIGS. 11 to 13 show an embodiment of a method for grounding a wafer to be inspected. FIG. 11 shows a method of grounding by bringing a needle into contact with the back surface of the wafer. As shown in FIG. 11, grooves are formed in the wafer chuck 24, and needles 25 are arranged so as to uniformly contact the entire back surface of the wafer, and these are kept at the ground potential. Since the entire back surface can be uniformly contacted with a plurality of needles, uneven charging in the wafer to be inspected can be prevented.

FIG. 12 shows a method in which the needle is brought into contact with the upper surface of the wafer, and the needle 35 maintained at the ground potential is set at an appropriate position on the sample surface. Depending on the method of chucking the wafer, the wafer may be fixed by a method that does not apply a downward force to the wafer only by supporting from the measuring method. In such a case, the means shown in FIG. Cannot make sufficient contact with the needle. By bringing the needle into contact with the upper surface of the wafer, the sample can be kept at the ground potential regardless of the method of fixing the wafer.

FIG. 13 shows a method of bringing a knife edge into contact with a side surface of a wafer. A sharp knife-shaped edge 30 is brought into contact with the side surface of the wafer to be inspected and grounded, whereby the potential of the wafer is always kept at the ground potential. In this method, the wafer to be inspected can always be kept at the ground potential without damaging the upper surface of the wafer, regardless of the method of fixing the wafer. These means are appropriately selected according to the wafer chucking method and the like.

Next, a description will be given of a second embodiment of the inspection method using the inspection apparatus of FIG.

In the first embodiment, the inspection is performed by constantly irradiating the inspection region with an electron or ion shower during the inspection. In this embodiment, the inspection is performed by changing the timing of these irradiations. FIG. 14 shows an example of the state of charges when two arbitrary areas on a wafer to be inspected are inspected. As shown in FIG. 14B), the electron beam irradiation on the inspection area D after the inspection of the inspection area D37 causes uneven charging on the wafer to be inspected, and also changes the charging state of the next inspection area E38. . When the electron beam image of the area E is input in the state of FIG. 14B), the charged state at the time of inspection differs between the area D and the area E.
Changes in brightness and the like also occur in the obtained image, making comparison inspection difficult.

As a means for solving such a problem, in this embodiment, an electron beam image is input in the procedure shown in FIG.
In FIG. 5, it is assumed that the inspection is performed under the condition 26 of the primary electron acceleration energy at which the secondary electron emission ability becomes 1 or more. Before inputting the electron beam image of the inspection region D, the inspection region D is irradiated with the electron shower 28, the surface of the sample is negatively charged by the electric charge 39 to be saturated, and after the irradiation of the electron shower is completed once, the inspection region D Enter an image. Next, the inspection area E is irradiated with the electron shower 28, and the surface of the sample is negatively charged by the electric charge 40 to be in a saturated state. Then, the irradiation of the electron shower is terminated, and the image of the inspection area E is input. By starting image input in a state where the charge on the sample surface is always saturated in this way, the obtained electron beam image is always an image under the same charge condition. The irradiation range and timing of the electron shower are appropriately changed according to the positional relationship between the plurality of inspection regions and the size thereof.

In this embodiment, since the irradiation of the electron shower is not performed at the time of inputting the electron beam image, the energy filter 33 by the mesh electrode 22 becomes unnecessary. Similarly, in FIG. 5, when the inspection is performed under the condition 33 of the primary electron acceleration energy at which the secondary electron emission ability becomes 1 or less, the irradiation of the ion shower 30 may be performed instead of the electron shower 29.

Next, a description will be given of a third embodiment of the inspection method to which the inspection apparatus of FIG. 4 is applied.

In the second embodiment described above, the inspection is performed after the charged state of the inspection area is saturated in advance, but in this embodiment, the electron beam image obtained during the inspection is processed to
The charged state of the sample is monitored, and the charged state is controlled by irradiating an electron or ion shower according to the state.

Consider a case in which electron beam images are continuously obtained in the order shown in FIG.

It is assumed that the pattern to be inspected in FIG. 4 is inspected under the condition 26 that the secondary electron emission ability is 1 or more. FIG. 16B) shows an example of the change of the brightness of the circuit pattern of the obtained electron beam image at the inspection time t.

Reference numeral 41 denotes a case in which an electron beam is input without controlling the charging. Since the secondary electron emission capability is 1 or more, the surface of the sample pattern is charged up positively by the scanning of the electron beam, and the inspection time At the same time, the brightness of the image changes. As described above, since the brightness of the electron beam image changes with the change in the state of charging, in this embodiment, the state of charging of the inspection object is monitored based on the brightness of the image, and as shown in FIG. The inspection is performed while controlling the charged state so as to keep the brightness of the pattern constant.

FIG. 17 shows the details of the control method of the charged state. The secondary electronic video signal 43 input from the image input unit 16 is processed to obtain the brightness 44 of the circuit pattern. The target brightness 45 of the circuit pattern set in advance is compared with the brightness 44 of the detected pattern, and the irradiation amount 47 of the electron shower is determined based on the difference 46. In the example of FIG. 16, since the image is darkened by the pattern being positively charged, if the detected brightness is smaller than the target value, the electron shower is irradiated with an amount corresponding to the difference. Not performed.

As described above, by obtaining a change in the state of charge from the electron beam image and determining the irradiation amount of the electron shower,
As shown in Fig. 16b) 42, the state of the electron beam image can be kept constant, and a stable inspection can be realized. Here, the brightness 44 of the electron beam image of the circuit pattern is obtained by dividing the obtained electron beam image into a circuit portion and a base portion, and calculating the average brightness of only the circuit pattern portion.

In this embodiment, the brightness of the circuit portion is used. However, as parameters reflecting the charging state of the inspection object, the average of the entire electron beam image, the contrast between the circuit portion and the base portion, and the circuit portion and the base portion are used. A similar function can be realized by using a change in the area of the section. The target value 45 of the brightness of the pattern to be used is set to an appropriate value based on an electron beam image of the pattern to be inspected in advance and the brightness of the electron beam image.

Generally, as shown in FIG. 16 b) 41, the brightness of the electron beam image changes sharply immediately after the start of electron beam irradiation. The magnitude of this change and the time constant vary depending on the sample, but in order to perform stable control, it is desirable to set the target value of brightness so as to avoid this rapidly changing range. At this time, a more stable inspection can be realized by setting the brightness of the electron beam image at the start of the inspection to a value sufficiently close to the set target value. In order to start an inspection with an electron beam image having a brightness sufficiently close to the target value, input of an electron beam image is started in a state 41 in which the charge state is not controlled, and a change in the brightness of the electron beam image is monitored. Then, after sufficiently approaching the target value (time t13), the charging state may be controlled to the state of 42, and the inspection may be started.

In order to more reliably approach the target value, the sample to be inspected may be irradiated with an ion shower before the start of the inspection so that the electron beam image becomes the target value set at the start of the inspection. As shown in (b) of FIG. 16, when the ion shower is irradiated at time t11 and the brightness of the electron beam image reaches the target value (time t12), the inspection is started. In this way, the inspection can be always performed in the same charged state from the start of the inspection.

Similarly, in FIG. 5, the secondary electron emission ability is 1
When the inspection is performed under the following conditions 27 of the primary electron acceleration energy, irradiation with an ion shower may be performed instead of the electron shower, and more stable inspection is realized by using the electron shower at the start of the inspection. can do.

Next, a description will be given of a fourth embodiment of an inspection method for preventing charge-up of a sample by a method different from that of the first embodiment. In an electron microscope, if the degree of vacuum in the sample chamber is low, contamination of the sample surface by residual gas molecules becomes a problem. Therefore, the degree of vacuum in the sample chamber is usually kept at a high vacuum. When gas is introduced into the sample chamber and the degree of vacuum in the sample chamber is reduced (when the pressure is increased), the mean free path of the incident electrons is shortened, and the gas molecules that collide with some of the incident electrons and are ionized are ionized. Increase. Therefore, when an inert gas or a nitrogen gas is introduced into the sample chamber to be in a low vacuum (vacuum state in which the pressure is higher than a normal electron beam irradiation atmosphere) or an atmospheric pressure state, positive ions generated by collision with incident electrons are generated. Thereby, electrons on the sample surface are neutralized and charging can be prevented. By using an inert gas or a nitrogen gas as a gas to be introduced, a low vacuum without sample contamination can be realized.

The details of this embodiment will be described with reference to FIG. The sample chamber is set as a differential exhaust chamber 48, and a rare gas such as Ar, Kr, Ne or the like is supplied from a gas cylinder 49 to maintain the degree of vacuum in the sample chamber at a low vacuum of about 10-3 to several Pa. At this time, the electron optical system is kept in a high vacuum. Ar, Kr, N
Since rare gases such as e have a small physical adsorption energy, contamination of the sample surface can be prevented by setting the sample chamber to such a gas atmosphere. In this way, low vacuum is realized without contamination of the sample, and the charge on the surface of the sample is neutralized by the ionized residual molecules. Can be.

Although FIG. 18 shows a structure in which the pressure of the whole sample chamber is increased by the introduced rare gas, the rare gas is supplied to the wafer 1 to be inspected by using a nozzle connected to a pipe from a gas cylinder. The same effect can be obtained by locally supplying the electron beam 8 at the above-mentioned pressure or a higher pressure to the vicinity thereof, and by locally increasing the pressure near the electron beam 8 to the irradiation position. Can be obtained. In this case, the pressure in the sample chamber can be kept low and the amount of gas introduced into the sample chamber can be reduced as compared with the case where gas is introduced into the entire sample chamber, and contamination inside the sample chamber can be reduced. Can be less.

Further, as a fifth embodiment, an embodiment of an inspection for preventing charging of a sample by means using plasma at the time of detecting reflected electrons will be described.

If a plasma is generated in the sample chamber and the wafer to be inspected is placed in the plasma, the positive and negative charges in the plasma neutralize the charges on the sample surface, thereby preventing the charge. Since electrons having various energies exist in the plasma, it is difficult to separate these electrons from secondary electrons. In the present embodiment, a description will be given of a means for forming an energy filter 34 by the mesh electrode 22 and detecting only reflected electrons having high energy.

As shown in FIG. 19, the sample chamber is set as a differential pumping chamber 48 and a rare gas atmosphere such as Ar is used. The ECR point is formed by the magnet 50, and the frequency is
A microwave 52 around 2.45 GHz is generated, and a plasma 53 is generated in the sample chamber. In order to separate the electrons present in the plasma from the reflected electrons generated by the electron beam irradiation, the energy of the plasma is suppressed to less than the reflected electrons, a voltage is applied to the mesh electrode 22 to form an energy filter 34, and only the reflected electrons 54 are formed. It is detected by the backscattered electron detector 55. By such means, it is possible to always obtain a reflected electron image in a stable state without charge-up of the sample.

By employing the means described above, it is possible to prevent the charge-up from affecting the electron beam image when observing or inspecting a sample using a scanning electron microscope. , A stable electron beam image can be obtained. as a result,
With a scanning electron microscope, it becomes possible to observe and inspect a fine pattern on a sample with high definition and high reproducibility.

In particular, according to the present invention, when comparing a plurality of temporally different electron beam images obtained by observing the same position on a sample with a scanning electron microscope, and when comparing the same pattern at a different position on the sample or a corresponding pattern. When comparing a plurality of electron beam images obtained by observing a pattern, a stable electron beam image that is not affected by charge-up can be obtained, so that highly reliable comparison can be performed.

[0057]

According to the present invention, it is possible to input an electron beam image under the same condition of the charged state of a sample even in a long-time inspection, so that an electron beam image with good reproducibility is always obtained. be able to. Therefore, even when an electron beam image captured at a long interval or an electron beam image captured between different wafers is used, complicated processing such as edge detection and position shift tolerance is not required, and an optical microscope is used. An inspection similar to the inspection based on the pattern comparison principle, which is often used in the inspection, can be performed, and a long-time stable and highly sensitive inspection can be performed. Since an electron beam image can realize higher resolution than a conventional optical microscope, it is possible to realize an inspection apparatus that can be applied to a semiconductor device that is being miniaturized.

Further, by realizing a stable long-term inspection without time fluctuation, it becomes possible to perform a defect distribution in a wafer, an inspection between wafers, a monitor of a semiconductor manufacturing process, and the like. This makes it possible to estimate the cause of the occurrence of a defect in the semiconductor device and take an early action, thereby contributing to an improvement in yield.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating a manufacturing process of a semiconductor device.

FIG. 2 is a diagram showing a change in an electron beam image due to a charging phenomenon.

FIG. 3 is a cross-sectional view of a sample showing a change in a charged state of the sample by scanning with an electron beam.

FIG. 4 is a schematic cross-sectional view of a semiconductor device inspection apparatus according to the present invention.

FIG. 5 is a diagram showing the dependence of the secondary electron emission capacity and beam diameter on the primary electron acceleration energy.

FIG. 6 is a cross-sectional view of a sample showing an irradiation state of an electron shower on the sample according to the present invention.

FIG. 7 is a sectional view of a sample showing an irradiation state of an ion shower on the sample according to the present invention.

FIG. 8 is a schematic sectional view of an inspection apparatus provided with an electronic shower according to the present invention.

FIG. 9 is a diagram showing an energy distribution of emitted electrons.

FIG. 10 is a schematic sectional view of an inspection apparatus provided with an ion shower according to the present invention.

FIG. 11 is a schematic cross-sectional view of a wafer to be inspected, a wafer chuck, and a sample stage showing a method for grounding the wafer to be inspected according to the present invention.

FIG. 12 is a schematic cross-sectional view of a wafer to be inspected, a wafer chuck, and a sample table showing a grounding method of the wafer to be inspected according to the present invention.

FIG. 13 is a schematic cross-sectional view of a wafer to be inspected, a wafer chuck, and a sample table showing a method for grounding the wafer to be inspected according to the present invention.

FIG. 14 is a plan view of the wafer to be inspected, showing a state of charges on the wafer to be inspected.

FIG. 15 is a plan view of a wafer to be inspected showing an input order of electron beam images on the wafer to be inspected according to the present invention.

FIG. 16 (a) is a plan view of a wafer to be inspected showing an input order of electron beam images on the wafer to be inspected according to the present invention. b) A diagram showing a change in brightness of the circuit pattern of the electron beam image at the inspection time t.

FIG. 17 is a flowchart illustrating a charging state control method according to the present invention.

FIG. 18 is a schematic sectional view of an inspection apparatus showing a fourth embodiment according to the present invention.

FIG. 19 is a schematic sectional view of an inspection apparatus showing a fifth embodiment according to the present invention.

[Explanation of symbols]

1 ... wafer to be inspected, 8 ... electron beam, 9 ... beam scanning, 12 ... pattern, 13 ... electron source, 14 ... polarizer, 15 ... secondary electron detector, 16 ... image input Department,
19 ... Image processing unit, 20 ... Control computer, 21 ...
... Electronic shower generator, 22 ... Mesh electrode, 23 ...
... Ion shower generator, 24 ... Wafer chuck, 2
5 ... Needles, 26 ... Primary electron acceleration energy region where secondary electron emission ability is 1 or more, 27 ... Primary electron acceleration energy region where secondary electron emission ability is 1 or less, 28 ... Electron shower, 30 …… Ion shower, 32 …… Secondary electron, 3
3 ... Energy filter, 36 ... Knife edge, 3
9: charge, 41: 42 when charge state is not controlled
... When controlling the charged state, 43... Secondary electronic image signal, 44... Circuit pattern brightness, 45... Circuit pattern brightness target value, 46... Difference from the target value, 47.
... Electron shower dose, 48 ... Differential exhaust chamber, 4
9 ... gas cylinder, 50 ... magnet, 51 ... oscillator, 52 ... microwave, 53 ... plasma, 54 ...
Backscattered electrons, 55 Backscattered electron detector

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Asahiro Kuni 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Research Institute of Industrial Technology, Hitachi, Ltd. Address: Within Hitachi, Ltd., Production Technology Research Laboratories (72) Junzo Higashi Inventor: 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture 292 Hitachi Manufacturing Co., Ltd.Production Technology Laboratory (72) Inventor Kaoru Osoya 2326 Imai Imai, Ome-shi, Tokyo Inside Device Development Center, Hitachi, Ltd.

Claims (17)

[Claims] 1. A method for inspecting a semiconductor device using an electron beam image, comprising: controlling an electrification state of a region to be inspected of the semiconductor device; Irradiating an area, detecting secondary electrons generated from the inspected area by the irradiation of the electron beam to obtain a secondary electron image of the inspected area, and based on the secondary electron image, A method for inspecting a semiconductor device, comprising: inspecting an appearance of a circuit pattern of the semiconductor device formed in a region to be inspected. 2. A method for inspecting a semiconductor device using an electron beam image, wherein the inspection region of the semiconductor device is irradiated with an electron beam, and secondary electrons generated from the inspection region by the irradiation of the electron beam. To obtain a secondary electron image of the inspection area, monitor the charging state of the inspection area based on the secondary electron image, and determine the charging state of the inspection area based on the monitored result. Controlling the state, and inspecting the appearance of the circuit pattern of the semiconductor device formed in the inspection area of the semiconductor device based on the secondary electron image in a state where the charging state is controlled. For testing semiconductor devices. 3. The inspection of a semiconductor device according to claim 1, wherein the control of the charging of the inspection area of the semiconductor device is performed by using a means that does not contact the semiconductor device. Method. 4. The semiconductor device inspection method according to claim 3, wherein the non-contact means is performed by irradiating the inspection area with electrons in a shower shape. 5. The semiconductor device inspection method according to claim 3, wherein the non-contact means is performed by irradiating the inspection area with ions in a shower shape. 6. The semiconductor device inspection method according to claim 3, wherein the non-contact means is performed by introducing a gas into the vicinity of the inspection area. 7. The semiconductor device inspection method according to claim 3, wherein the non-contact means is performed by generating a plasma near the inspection area. 8. The inspection method of a semiconductor device according to claim 1, wherein the control of the charging of the inspection area of the semiconductor device is performed using a unit that contacts the semiconductor device. . 9. A method for inspecting a semiconductor device using an electron beam image, comprising: saturating at least a region to be inspected of the semiconductor device before irradiation with an electron beam; Irradiating the inspected area with the electron beam, detecting secondary electrons generated from the specimen area by the irradiation of the electron beam, and forming a secondary electron image of the inspected area from the detected secondary electrons. Obtaining a surface of the semiconductor device formed in the inspection area based on the secondary electron image. 10. An inspection apparatus for a semiconductor device using an electron beam image, comprising: an electron beam irradiation means for scanning and irradiating an electron beam focused on a region to be inspected of the semiconductor device; A charge control unit for controlling a state of charging; a secondary electron generated from the inspection region by the electron beam irradiated to the inspection region by the electron beam irradiation unit; and a secondary electron in the inspection region. A secondary electron image forming means for forming an image; and the electron beam irradiating means irradiating the inspection area with the electron beam in a state where charging of the inspection area is controlled by the charging control means. A semiconductor inspection apparatus for inspecting an external appearance of a circuit pattern of the semiconductor device formed in the inspection area based on a secondary electron image obtained by an image creating means. 11. An apparatus for inspecting a semiconductor device using an electron beam image, comprising: an electron beam irradiating means for irradiating an inspection area of the semiconductor device with an electron beam; The secondary electrons generated from the inspection area are detected to detect the secondary electrons.
Secondary electron image creating means for creating a secondary electron image; and charge monitoring means for monitoring the state of charging of the inspection area based on the secondary electron image of the inspection area created by the secondary electron image creating means Charge control means for controlling the charging state of the inspection area based on the charging state of the inspection area monitored by the charging monitoring means; and charging of the inspection area is controlled by the charging control means. And inspecting the appearance of a circuit pattern of the semiconductor device formed in the inspection area of the semiconductor device on the basis of the secondary electron image in a state where the semiconductor device is inspected. apparatus. 12. An inspection apparatus for a semiconductor device according to claim 10, wherein said charging control means controls charging of said inspection area without contacting said semiconductor device. 13. An inspection apparatus for a semiconductor device according to claim 12, wherein said charge control means is an electron shower irradiation means for irradiating said inspection area with electrons in a shower shape. 14. An inspection apparatus for a semiconductor device according to claim 12, wherein said charging control means is an ion shower irradiation means for irradiating said inspection target area with ions in a shower shape. 15. The inspection apparatus for a semiconductor device according to claim 12, wherein said charging control means is a gas introduction means for introducing a gas into the vicinity of said inspection area. 16. An inspection apparatus for a semiconductor device according to claim 12, wherein said charging control means is a plasma generation means for generating a plasma near said inspection area. 17. An inspection apparatus for a semiconductor device according to claim 10, wherein said charging control means controls charging of said inspection area by contacting said semiconductor device.